Dielectric relaxation phenomena of rigid polar liquid molecules under giga hertz electric field

The dielectric relaxation phenomena of rigid polar liquid molecules chloral and ethyltrichloroacetate (j) in benzene, n-hexane and n-heptane (i) under 4.2, 9.8 and 24.6 GHz electric fields at 30°C are studied to show the possible existence of double relaxation times τ ₂ and τ ₁ for rotations of the whole and the flexible parts of molecules. The probability of showing double relaxation is more in aliphatic solvents indicating their nonrigidity. The symmetric and asymmetric distribution parameters γ and δ are obtained from X _ij ^′ /X _0ij and X _ij ^″ /X _0ij and w _j →0 where X _ij ^′ and X _ij ^″ are real and imaginary parts of the complex orientational susceptibility X _i ^* and X _0ij is the low frequency susceptibility which is real. X _ij ’s are involved with the measured dielectric relative permittivities ε _ij ^′ , ε _in ^″ , ε _0ij and ε _∞ij of solutions. The theoretical weighted contributions c ₁ and c ₂ towards dielectric dispersions by Fröhlich’s method are compared with the experimental ones obtained from the graphical variation of X _ij ^′ /X _0ij and X _ij ^″ /X _0ij with weight fractions w _j ’s at w _j → 0. The measured dipole moments μ ₂ and μ ₁ of the whole and the flexible part of a polar molecule in terms of the linear coefficients β’s of X _ij ^′ ’s with w _j ’s and the estimated τ ₂ and τ ₁ reveal their associations with aliphatic solvents. The theoretical dipole moments μ _theo’s from the available bond angles and bond moments of the substituent polar groups of the molecules with the estimated μ’s suggest the mesomeric, inductive and electromeric effects in them under GHz electric field.     

Upper and lower error bounds for plate-bending finite elements

Summary. We compare the robustness of three different low-order mixed methods that have been proposed for plate-bending problems: the so-called MITC, Arnold-Falk and Arnold-Brezzi elements. We show that for free plates, the asymptotic rate of convergence in the presence of quasiuniform meshes approaches the optimal O(h) for MITC elements as the thickness approaches 0, but only approaches for the latter two. We accomplish this by establishing lower bounds for the error in the rotation. The deterioration occurs due to a consistency error associated with the boundary layer – we show how a modification of the elements at the boundary can fix the problem. Finally, we show that the Arnold-Brezzi element requires extra regularity for the convergence of the limiting (discrete Kirchhoff) case, and show that it fails to converge in the presence of point loads. Received June 9, 1998 / Published online December 6, 1999     

Online Scheduling with Hard Deadlines

We study non-preemptive, online admission control in the hard deadline model: each job must either be serviced prior to its deadline or be rejected. Our setting consists of a single resource that services an online sequence of jobs; each job has a length indicating the length of time for which it needs the resource and a delay indicating the maximum time it can wait for the service to be started. The goal is to maximize total resource utilization. The jobs are non-preemptive and exclusive, meaning once a job begins, it runs to completion, and at most one job can use the resource at any time. We obtain a series of results, under varying assumptions of job lengths and delays.     

Selective identification of specific aptamers for the detection of non-typhoidal salmonellosis in an apta-impedimetric sensing format

Microchimica Acta - The authors report on an aptamer-based method for the detection of S. Typhimurium. The aptamers were identified by using a modified cell-based SELEX method (cell-SELEX) by...     

Gold nanoparticles catalyzed chemiluminescence immunoassay for detection of herbicide 2,4-dichlorophenoxyacetic acid

We present a novel immunoassay format utilizing the catalytic properties of gold nanoparticles in the luminol-silver nitrate-gold nanoparticle based chemiluminescence (CL) system for the detection of widely used herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Highly sensitive anti-2,4-D antibody was produced and conjugated with gold nanoparticles of various sizes. In the present assay format, employing a competitive inhibition approach, a well-characterized hapten-protein conjugate (2,4-D-BSA) was used to coat the microtiter plates. The analyte (2,4-D) was pre-incubated with anti-2,4-D antibody labeled with gold nanoparticles and added to each well of the microtiter plate. The gold label triggered the reaction between luminol and silver nitrate generating a luminescence signal at 425 nm. Under the optimized conditions, the CL based immunoassay showed the detection limit of 2,4-D in standard water samples around 3 ng mL(-1). The CL based immunoassay format, based on gold nanoparticles as a catalyst, could be used as a fast screening methodology (<30 min) for pesticide detection.     

Combined molecular dynamics and continuum solvent approaches (MM-PBSA/GBSA) to predict noscapinoid binding to γ-tubulin dimer

γ-tubulin plays crucial role in the nucleation and organization of microtubules during cell division. Recent studies have also indicated its role in the regulation of microtubule dynamics at the plus end of the microtubules. Moreover, γ-tubulin has been found to be over-expressed in many cancer types, such as carcinomas of the breast and glioblastoma multiforme. These studies have led to immense interest in the identification of chemical leads that might interact with γ-tubulin and disrupt its function in order to explore γ-tubulin as potential chemotherapeutic target. Recently a colchicine-interacting cavity was identified at the interface of γ-tubulin dimer that might also interact with other similar compounds. In the same direction we theoretically investigated binding of a class of compounds, noscapinoids (noscapine and its derivatives) at the interface of the γ-tubulin dimer. Molecular interaction of noscapine and two of its derivatives, amino-noscapine and bromo-noscapine, was investigated by molecular docking, molecular dynamics simulation and binding free energy calculation. All noscapinoids displayed stable interaction throughout simulation of 25 ns. The predictive binding free energy (ΔG_bind) indicates that noscapinoids bind strongly with the γ-tubulin dimer. However, bromo-noscapine showed the best binding affinity (ΔG_bind = –37.6 kcal/mol) followed by noscapine (ΔG_bind = –29.85 kcal/mol) and amino-noscapine (ΔG_bind = –23.99 kcal/mol) using the MM-PBSA method. Similarly using the MM-GBSA method, bromo-noscapine showed highest binding affinity (ΔG_bind = –43.64 kcal/mol) followed by amino-noscapine (ΔG_bind = –37.56 kcal/mol) and noscapine (ΔG_bind = –34.57 kcal/mol). The results thus generate compelling evidence that these noscapinoids may hold great potential for preclinical and clinical evaluation.     

Optimization of synthetic parameters for Tl-2201 superconducting phase by flash sintering process

Samples with nominal composition Tl₂Ba₂Cu_1.2 (copper-rich Tl-2201) were calcined at various temperature, i.e. from 865 °C to 910°C and for various durations (10–20 h). The samples were sintered for 31/2 min at various temperatures. The X-ray powder diffraction pattern indicates that most of the Tl-Ba-Cu samples (Tl-2201) are single-phase materials. All the lines in the X-ray pattern are indexable on a tetragonal unit cell showing tetragonal symmetry having space group 14/mmm with a=3.86 Å C=23.11 ± 0.06 Å as unit cell parameters. R−T and AC susceptibility measurements show T^on_c, from 90 to 104 K. There is an elongation of the c-axis (c=23.24 Å) for the sample showing the highest T_c. Wet chemical analysis confirms the deficiency of thallium. This suggests some substitution of Cu in place of thallium which leads to an increase in the average oxidation state of copper, responsible for the creation of holes (charge carriers).     

Two-color photoionization spectroscopy of uranium in a U–Ne hollow cathode discharge tube

A U–Ne hollow cathode discharge tube is used as a source of uranium atomic vapors as well as a photoelectron/photoion detector for carrying out two-color three-photon photoionization spectroscopy of uranium. Using the uranium excitation transition 0 cm⁻¹ (⁵L ₆ ⁰ ) → 16 900.38 cm⁻¹ (⁷M₇) at 591.5-nm laser wavelength as a first step transition and scanning the wavelength of a second laser from 558 to 568 nm, high-lying odd-parity atomic levels of uranium are studied in the energy region 34 500–34 813 cm⁻¹. All the expected 21 odd-parity atomic levels identified by various researchers in this region are observed in a single spectrum, demonstrating the high sensitivity achieved therein. In addition to this, we have identified eight autoionization resonances of uranium starting from its odd-parity atomic level at 33 801.06 cm⁻¹ pumped by two-photon excitation. Four out of these eight autoionization resonances are observed for the first time.     

Can visibility graphs Be represented compactly?

We consider the problem of representing the visibility graph of line segments as a union of cliques and bipartite cliques. Given a graphG, a familyG={G ₁,G ₂,...,G _k } is called aclique cover ofG if (i) eachG _i is a clique or a bipartite clique, and (ii) the union ofG _i isG. The size of the clique coverG is defined as ∑ _i=1 ^k n _i , wheren _i is the number of vertices inG _i . Our main result is that there are visibility graphs ofn nonintersecting line segments in the plane whose smallest clique cover has size Ω(n ²/log² n). An upper bound ofO(n ²/logn) on the clique cover follows from a well-known result in extremal graph theory. On the other hand, we show that the visibility graph of a simple polygon always admits a clique cover of sizeO(nlog³ n), and that there are simple polygons whose visibility graphs require a clique cover of size Ω(n logn). The work by the first author was supported by National Science Foundation Grant CCR-91-06514. The work by the second author was supported by a USA-Israeli BSF grant. The work by the third author was supported by National Science Foundation Grant CCR-92-11541.     

Applications of a semi-dynamic convex hull algorithm

We obtain new results for manipulating and searching semi-dynamic planar convex hulls (subject to deletions only), and apply them to derive improved bounds for two problems in geometry and scheduling. The new convex hull results are logarithmic time bounds for set splitting and for finding a tangent when the two convex hulls are not linearly separated. Using these results, we solve the following two problems optimally inO(n logn) time: (1) [matching] givenn red points andn blue points in the plane, find a matching of red and blue points (by line segments) in which no two edges cross, and (2) [scheduling] givenn jobs with due dates, linear penalties for late completion, and a single machine on which to process them, find a schedule of jobs that minimizes the maximum penalty.